Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $73.25   4.649%   $76.6554   $76.66   $76.65   $76.70  
  Purchase #2 $228.49   6.295%   $242.8734   $242.87   $242.85   $242.90  
  Purchase #3 $163.62   7.666%   $176.1631   $176.16   $176.15   $176.20  
  Purchase #4 $209.51   5.668%   $221.385   $221.39   $221.40   $221.40  
  Purchase #5 $166.95   6.159%   $177.2325   $177.23   $177.25   $177.20  
  Purchase #6 $76.58   11.722%   $85.5567   $85.56   $85.55   $85.60  
  Purchase #7 $176.80   7.565%   $190.1749   $190.17   $190.15   $190.20  
  7 purchase totals = $1,095.20       $1,170.0410   $1,170.04   $1,170.00   $1,170.20